The invention relates generally to condition monitoring and diagnostics of wiring systems and, more particularly, to condition monitoring and diagnostics of aircraft wiring systems using partial discharge analysis (“PDA”).
An exemplary wire for an aircraft wiring system is shown in FIG. 1 and includes a conductive core, which is surrounded by insulation. The insulation may be surrounded by a sheath. There are three primary failure modes for wires in aircraft wiring systems: loose connectors, corrosion of a connecter, and damaged insulation. Damage to insulation takes two forms: material degradation due to aging or thermal/electrical environment, and chafing, which may occur during maintenance.
To detect wire failure in aircraft systems, wiring is presently monitored using either time or frequency domain reflectometry (TDR or FDR, respectively). Although these techniques improve upon simple impedance testing, by permitting identification and localization of hard wiring failures, they are unable to monitor degradation associated with the insulation and corrosion. Currently, degradation of insulation and corrosion are typically identified during visual inspection. Other shortcomings of TDR and FDR include the fact that they are performed offline, that is when the aircraft is out of service, their inability to predict wire failures and to identify potential sources of damage (electrical, thermal, mechanical, or environmental) that may lead to a wire failure on later flights, and their lack of sensitivity.
Adverse consequences of these inspection shortcomings include the expenditure of numerous man-hours for troubleshooting to identify sources of damage, as well as the removal and replacement of functioning equipment due to erroneous failure detection or prediction. Given the associated increased maintenance time and cost, there is a need for an improved monitoring system and method for aircraft wiring that is capable of monitoring the degradation associated with the insulation and corrosion, before failure occurs.
Partial discharge analysis has been successfully used to evaluate the integrity of high voltage insulation systems in the electrical industry. Briefly, partial discharges (“PD”) are generated during the initial (and subsequent) stages of insulation breakdown, as well as in response to arcing between connectors, in a wide variety of electrical components, such as generators, transformers, capacitors, circuit board, wiring, and medical equipment. The analysis of partial discharges via spectrum analysis, phase resolution, or pattern recognition (or combinations thereof) is generally known as partial discharge analysis. By examining the evolution of partial discharges over time, failures can be predicted, and equipment failure can thus be avoided.
Accordingly, it would be desirable to develop a method and system for monitoring the condition of an aircraft wiring system that employ partial discharge analysis.